Three decades into the epidemic, HIV continues to be a major public health problem. Many behavioral interventions have been shown to be effective at changing risk behaviors in controlled research environments. Efforts have also increased for moving evidence-based interventions (EBIs) from research to practice as part of federal initiatives such as the CDC's Diffusion of Effective Behavioral Interventions and SAMHSA's National Registry of Effective- based Programs and Practices. Limited research has examined the implementation processes of these interventions, especially peer education interventions in community settings. It is important to understand which interventions can effectively and cost-effectively implement the EBIs in real-world settings Up until this point in my career, my research has focused on identifying risk and protective factors for HIV in the social environment, specifically social networks. In addition, I have developed and evaluated behavioral interventions for at risk groups. My long-term career goal is to develop and disseminate cost-effective, sustainable interventions, in partnership with community agencies and to study their implementation process. My short-term goal, which is discussed in this Mentored Scientist K01 application, is to acquire mentoring, knowledge, and practical experience in the theories, study designs, and methodologies of 1) dissemination and implementation science to identify strategies to disseminate and study the implementation of evidenced-based interventions in real-world settings; 2) community engagement research to partner with community agencies in intervention development, dissemination, and implementation; and 3) economic evaluation methods to assess the costs of implementing interventions. My training goals are to 1) Obtain background in the empirical literature and theories/framework that guide dissemination and implementation of behavioral interventions in community settings. 2) Gain skills and knowledge in methodology, such as study design, measurement, and data collection, to study the implementation of interventions in community settings. 3) Acquire knowledge and application of theories and methods for community-engaged research and developing community partnerships for dissemination and implementation of interventions. 4) Become proficient in economic evaluations of the costs required to implement behavioral interventions in community settings. These goals will be achieved through mentor meetings, coursework and tutorials, webinars/seminars, directed readings, conferences, and a journal club. As a result of this career development award, I will become an independent researcher who develops and disseminates HIV prevention interventions through collaborations with community agencies for implementation in practical settings. The proposed research project will focus on a peer educator intervention for former and current drug users (The SHIELD intervention) that has been nationally disseminated by the CDC. The specific aims are to 1) examine organization, provider/staff, and intervention factors associated with stages of implementation of a social- network based peer education interventions (the SHIELD intervention); 2) investigate the relationships between barriers and facilitators and stages of implementation and explore strategies to overcome barriers to implementation; and 3) conduct an analysis of the agency and client costs associated with implementing a peer education intervention in community- based settings. These aims will be achieved by examining implementation among a nationally representative sample of community agencies (n=60) that have been trained to conduct the SHIELD intervention. Telephone interviews will be conducted with the Organization Leaders (i.e. Executive Directors) of agencies to assess stages of implementation of SHIELD and multi-level features associated with implementation as well as barriers and facilitators. An analysis of the costs associated with participation in the SHIELD intervention will also be assessed.